Defence Secretary Donald Rumsfeld is among those who are unlikely to last the full term, says the BBC's Justin Webb in Washington.

But because of the need for continuity on Iraq policy, the 72-year-old is expected to stay on for another year or so if he wants to.

The fate of Secretary of State Colin Powell is unclear. He is expected to go, but not everyone is convinced he wants to.

There is speculation he might be replaced by the recently appointed US ambassador to the UN, John Danforth.

National security adviser Condoleezza Rice has said in the past that she wants to return to her university career, but she is close to the president and is thought by some to harbour presidential ambitions herself.

She might be persuaded to stay on in another role, correspondents say.

There is speculation about other figures in the cabinet too. Attorney General John Ashcroft and Homeland Security Secretary Tom Ridge are likely to leave for personal reasons, the New York Times reports, citing administration officials.

Conservative agenda

Vice-President Dick Cheney has suggested the administration now has a mandate for a range of conservative social and economic policies.

These are likely to include issues ranging from tax reform to abortion and same-sex marriage.

President Bush will get the chance to appoint conservative justices to the Supreme Court if seats become vacant, which could have an impact far beyond his presidency.

The powerful nine-member court is able to take final decisions on issues ranging from the result of a presidential election to a woman's right to have an abortion.

The Republicans have strengthened their grip on the presidency and Congress, but they face continuing problems in Iraq, widespread foreign distrust and a huge budget deficit, says the BBC's Nick Childs in Washington.

World leaders were quick to respond to the news of Mr Bush's victory - some in warmer terms than others.

But many - including key allies - have warned that the US faces major challenges in the Middle East.

UK Prime Minister Tony Blair, a key ally, said: "The need to revitalise the Middle East peace process is the single most pressing political challenge in our world today."